1. Technical Field
The present invention relates to a light projector and a sensor. More specifically, it relates to a light projector configured to couple light from a light source to an optical fiber, as well as to a sensor provided with the light projector.
2. Background Art
Conventionally, a light projector including a light source and an optical fiber and configured to couple light from the light source to an end surface of the optical fiber has been known. If light emission from the light source spreads over a wide angle, only a part of the light from the light source enters the optical fiber, resulting in low coupling efficiency. Various techniques have been proposed to improve coupling efficiency.
By way of example, Japanese Patent Laying-Open No. 2005-24617 (Patent Document 1) discloses an optical transmitter capable of reducing fluctuation in transmission efficiency. In the optical transmitter, light emitted from a light emitting device is converted to collimated light beams by a lens and coupled to an optical fiber. Further, positional relation among the light emitting device, the lens and the optical fiber is set such that a light spot generated by the collimated light beams on an end surface of the optical fiber is larger than the area of core portion on that end surface. Because of such a configuration, even if the positions of light emitting device, lens and optical fiber should be deviated from designed positions, optical coupling efficiency between the light emitting device and the optical fiber is kept unchanged. Therefore, fluctuation in transmission efficiency can be reduced. Thus, worst value of transmission efficiency is improved and, as a result, transmission efficiency can be made higher.    Patent Document 1: Japanese Patent Laying-Open No. 2005-24617